Method of driving tunnels



March 19, 1968 M. F. KEMPER METHOD OF DRIVING TUNNELS 4 Sheets-Sheet l Original Filed May 23, 1963 March 19, 1968 M. F. KEMPER METHOD OF DRIVING TUNNELS 4 Sheets-Sheet 2 Original Filed May 23. 1963 M. F. KEMPER METHOD oF DRIVING TUNNELS Original Filed May 23. 1963 March A19, 1968 4 Sheets-Sheet 5 l A44/waa Aral/fe March 19, 1968 M. F. KEMPER METHOD OF DRIVING TUNNELS original Filed May 2s, 1963 4 Sheets-Sheetl wwf/waz /f/fa iff/14%? M@ am Armen/5% v United States Patent sinon? 9 claims. (Cl. 61-85) This application is a division of my application Ser. No. 282,771, tiled May 23, 196.3, for Method and Apparatus for Driving Tunnels and now Patent No. 3,250,078.

This invention relates to a novel method and apparatus for driving tunnels.

Apparatus of the type to which this invention relates is discolsed in my U.S. Letters Patent No. 2,997,853 issued Aug. 29, 1961, and includes an elongate arched shield adapted to be progressively driven into the earth while shiftably supported by a sereis of extensible jacks or legs likewise shiftably connected to the shield in order to be positioned best to support the shield for sustaining the load of the overburden in the operation of driving the tunnel.

It is desired in driving tunnels with apparatus generally of the type above described to provide in the shield as much working room as possible in the area adjacent the face of the tunnel for the men and equipment required in digging the tunnel, and at the same time to position the supporting jacks at locations assuring that the shield safely will sustain the load of the overburden in different types of ground, without tilting, sinking or otherwise moving o grade and so that accurate turns in the tunnel bore may be more readily made while remaining on grade.

It is an object vof this invention to provide a novel tunnel driving method which will achieve the above noted and other objectives of this invention in a particularly safe and efficacious manner.

lt is another object hereof to provide novel tunnel driving apparatus which readily lends itself to Carrying out the method hereof and constitutes an improvement in this art in that it includes a particularly novel construction and relative arrangement of the shield and supporting jacks making it possible to achieve the advantages herein noted.

A further object of this invention is to provide a novel method of driving a tunnel that is particularly safe and highly efficient by reason of including the steps of: positioning the shield so that it may be progressively driven into the tunnel face; positioning on each side of the longitudinal center line of the shield and at predetermined locations adjacent each side of the shield, a plurality of supports in contact with the ground and the upper part of the shield at longitudinally spaced locations on the latter; applying a force to move the shield relative to the supports and drive the shield into the tunnel face; and then repositioning said supports to prepare for the next drive of the shield, by lifting the supports one at a time from contact with the ground and shifting each support thus lifted itno a new supporting position relative to the shield while maintaining other of the plurality of supports on each side of the longitudinal center line of the shield in position to provide a reliable and safe support of the shield.

Further, it is an important object of this invention to provide novel tunnel driving apparatus of the character described wherein the elongate shield is provided with a pair of longitudinally extended tracks disposed in laterally spaced opposed relation on opposite sides of the longitudinal center line of the shield and adjacent the sides of the shield with a plurality of extensible ground-engage- 3,373,572 Patented Mar. 19, i968 able jacks slidably joined to each track so that when the jacks are in engagement with the ground, the shield may be moved or shifted relative to the jacks and be driven into the tunnel face. With this arrangement any one or more of the plurality of jacks on either side of the Shield may be shifted to a location best suited to support the shield according to the nature of the ground in which the shield is being driven, or a plurality of jacks may be grouped on one side of the shield at locations spaced laterally and longitudinally relative to a group of jacks on the opposite side of the shield or the jacks otherwise disposed, and in all cases so that when any one jack is out of engagement with the ground, at least one other jack of the plurality on each side of the shield will serve as an adequate support for the shield.

Another object of this invention is the provision of apparatus such as described wherein by reason of having the shield supported along each side of the longitudinal center thereof by a plurality of the jacks, it is possible to lengthen a jack on one side of the shield and to decrease the length of a jack on the other side of the shield in order to tilt or cant the shield to facilitate making a turn with the shield while maintaining it on grade and with the advantage of having other of the plurality of jacks on each side of the shield afford adequate support for the shield.

An additional object of this invention is the provision of tunnel driving apparatus such as described which in having a plurality of axially shiftable jacks close to each of the opposite side walls of the shield in rows extending longitudinally of the shield makes it unnecessary to provide a support or jack between the side jacks and thereby provides unobstructed working room at the face of the tunnel for men and equipment to the end that an efficient and comparatively economical tunnel digging operation may be carried out.

It is another object of this invention to provide in tunnel driving apparatus of the character described novel stabilizing means associated with the plurality of extensible legs on jacks on each side of the shield for stabilizing the legs or jacks and holding them from being moved while the shield is being advanced in the formation of the tunnel, this stabilizing means permitting each leg or jack to be intentionally independently moved into positions best to support the shield but operating to prevent movement of the legs while the shield is being advanced.

Other objects and advantages of the invention will be hereinafter described or will become apparent to those skilled in the art, and the novel features of the invention will be defined in the appended claims.

Referring to the drawings:

FIG. l is a longitudinal sectional View of apparatus embodying the present invention with the elements thereof, disposed `for driving the shield into the face of the tunnel relative tothe supporting jacks;

FIG. 2 is a view similar to FIG. 1 showing the positions occupied by elements of the apparatus after the shield has been driven a full stroke into the face of the tunnel, and indicating by the dot-dash showing of one of the jacks how the jacks may be repositioned to prepare the `apparatus for the next advance of the shield;

FIG. 3 is a transverse sectional view taken on the line 3 3 of FIG. 1;

FIG. 4 is a front elevation showing the apparatus substantially in the same position as shown in FIG. 1;

FIG. 5 is an enlarged vertical sectional view of one of the extensible jacks for supporting the shield, showing schematically in association therewith the hydraulic circuit and control means for each jack;

FIG. 6 is an enlarged detail view in section of the portion of the jacks to which the fluid lines are connected;

FIG. 7 is a fragmentary sectional view taken on the line 7-7 of FIG. 1, on an enlarged scale;

FIG. 8 is a fragmentary view of a modified form of extensible jack for supporting the shield showing the latter in section and the jack in elevation; and

FIG. 9 is an enlarged fragmentary sectional view of the jack shown in FIG. 8 including the schematic view of the hydraulic circuit and manually operable pump means for extending and retracting the jack.

Apparatus embodying the present invention includes an elongate steel shield A of horseshoe shape adapted to be driven into the earth as shown in FGS. l and 2, wherein F designates the face of the tun-nel being formed.

The forward [portion 1 of the shield is suitably reinforced preferably internally thereof and contains apparatus to be hereinafter described for driving the shield into the earth. The rear portion Z of the shield is adapted to extend as a protective shell over the tunnel lining or wall structure B that is erected progressively as the shield is advanced in the formation of the tunnel.

As here shown, the forward portion 1 of the shield is reinforced by means of longitudinally spaced arcuate plates 3 welded or otherwise fixed at their outer edges to the interior surface of the shield and projecting inwardly therefroml with their inner edges Welded to arched ribs d extending to the lower edges of the sides of the shield. I ust inside the downwardly and rearwardly inclined front end 5 of the shield are a series of triangular plates 6 welded to the inner surface of the shield and the foremost plates 3.

Means are provided for driving the shield into the earth and, as here shown, include four hydraulic rams 7 extended longitudinally of the interior of the front section 1 of the shield and securely fastened thereto in equidistantly spaced relation, there being a ram on each side of the top center portion of the shield and one on each side wall of the shield as will be apparent with reference to FIG. 3. The pistons 8 of the rams 7 extend rearwardly so as to contact the forward portion of the Wall assembly B which serves as a solid base structure against which the pistons bear in actuating the rams 7 to advance the shield. Any suitable means, not shown, may be employed for supplying and controlling the application of hydraulic fluid for operating the rams 7, it being preferable, however, to operate these rams in the manner and by the means shown in my copending application for patent, Ser. No. 678,993.

The wall or tunnel structure B, as here shown, may comprise a plurality of steel H-beams or ribs 9 that are erected in the rear or shell portion 2 of the shield as shown in FIGS. l and 2 with suitable lagging strips 10 installed between the beams. These beams and lagging strips are added to increase the length of the tunnel Wall structure B as the shield is advanced.

If a concrete lining for forming a conduit in the tunnel is to be provided, the lagging strips 10 when uncovered by advancing the shield so that the rear shell portion 2 exposes a large portion of the structure B, may serve as the outer wall of a concrete forms. However, in some instances, the structure B may be utilized as the supporting lining or wall of the tunnel and for the purpose of this description, it will be assumed that the foremost steel beam or rib 9 has been firmly installed. This firm installation of the foremost beam 9 is accomplished by use of jacks 11 as shown in FIG. 3, and the placing ofbase plates 12 under the beam whereby the structure B is forced against the inner surface of the rear portion 2 of the shell and is rmly secured in place, with provision, however, for the shield to be advanced relative thereto. Brace members 13 are positioned longitudinally on the structure B in line with the pistons 8 of the rams 7 and against the foremost rib 9 engaged by the pistons, these braces being securely attached in any suitable manner to the structure B so that a firm backing is provided for each piston to assure that the shield Will be advanced upon actuation of the rams 74.

In accordance with the invention, a plurality of longitudinally shiftable and extensible supporting members for the shield are located in a row in longitudinally spaced relation to one another against each side wall of the shield so as to leave a large unobstructed space between the sides of the shield at the face F of the tunnel for accommodating the digging apparatus and men required to dig the tunnel, while at the same time providing for a reliable support of the shield while the shield is advanced relative to the supporting members and at all other times during the operation of forming the tunnel. A particular advantage of this arrangement of supports is that they may be moved one at a time or otherwise into position best to brace the shield for supporting the over-burden in all types of ground, while at least one of the supports of the plurality on each side of the shield will be in shield supporting position during such movement of other of the supports. No center support is required for the shield while shifting the side supports as desired to prepare the shield for advance into the tunnel face, and no undesirable tilting of the shield which was occasioned at times with use of a center support, is permitted in view of the support of the shield on opposite sides of the longitudinal center line thereof.

The plurality of supports above referred to may consist, as here shown, -of a pair of extensible hydraulic jaclrs 15 disposed one ahead of the other on one side of the longitudinal center line of the shield and close to one side wall of the shield, while another pair of extensible jacks 16 is arranged in like manner on the other side of the shield. Obviously, more than two jacks may tbe provided on each side of the shield, the number of jacks required depending upon the size of the shield and the load it is required to sustain. When in supporting position, the jacks 15 and .t6 are rested on blocks 14.

As a means for mounting the jacks l5 and 16 so that the shield may be shifted relative thereto in being driven into the tunnel face and so that the jacks may be shifted longitudinally of the shield to reposition them as supports, longitudinally extending track assemblies 17 are welded or otherwise secured to the upper part of the forward portion l of the shield in laterally spaced relation to the longitudinal center line of the shield. Each track assembly 17 includes a plate 18 welded to and depending from the inner surface of the shield and provided at' its lower edge with a rail 19 welded thereto for supporting a carriage 2) having upper and lower sets of rollers 21 which ride on the top of the rail and on the lower side of the rail. Each carriage 20 supports one of the jacks which is pivoted thereto as at 22. With this arrangement the shield may be shifted relative to the jacks while the latter support the shield.

After an advance of the shield the jacks readily may be shifted longitudinally and repositioned as supports for the shield to prepare the shield for another advance into the tunnel face. The jacks may be swung on the pivotal connections thereof with the carriages 20 to out-of-theway positions when this is desired.

Means are provided for stabilizing the jacks or legs 15 and 16 to prevent them from being moved as the shield is being advanced. For this purpose the forward jack or leg on each side of the shield has a pair of rods 20a connected as at 20h to the carriage 20 of the jack and extended therefrom rearwardly along opposite sides of the carriage 20 of the next adjacent jack. At their rear ends the rods 20a have a cross member 20c fixed thereto and adapted to be secured by means of a hook 20d to a oable 20e. This cable leads to a comealong 20)c anchored as at 20g to the structure B. The rods 20a are slidably supported on a cross member 2011 fastened on the carriage 20 of the rearmost jack on each side of the shield. With this arrangement the rods 20a and cross member Ztlc comprise a frame or yoke D which embraces the plurality of jacks on each side of the shield yet permit free .movementof the tacks the desired extent best for snpporting the shield. As shown in FIGS. 1 and 7, when the jacks are positioned forwardly to support the shield for an advance into the tunnel face, the carriages abut one another and as the foremost carriage and its jack are restrained by the yoke D, cable 20e and comealong 20jc the plurality of jacks on opposite sides of the shield remain in upright position and lare held against being moved as the shield is advanced relative thereto. The comealong 20e may be operated as required to release the cable to allow the -foremost jack to be moved with the yoke D attached thereto. The come-along may be locked or tightened when the cable is taut [and the jacks are forwardly positioned. The length of the yoke D is such that the rearmost jack or a plurality thereof, if desired, may be independently moved therein as required best to support the shield. Thus, the yokes D at each side of the assembly and its come-along, constitute means for holding the forward jack against movement with the shield in .an advance direction as well as for `allowing independent longitudinal positioning of the respective rearward jacks.

Each of the jacks is constructed to be hydraulically extended and retracted whereby upon retraction from engagement with the ground, each jack may be shifted to the location where it is desired to provide a support for the shield and then extended into ground engaging position.

As here shown, each of the jacks 15 and 16 is of the same construction and includes a tubular body position 23 the upper end of which is pivoted as hereinbefore noted as at 22 to one of the carriages 20 and supports therein a xed piston unit 24 and a movable cylinder 25. This cylinder extends from the lower end of the body portion 23 and is closed at its upper and lower ends by an annular member 26 and a closure 27 respectively. The piston 23 of the piston unit 24 is disposed between the closed ends of the cylinder 25 with the piston rod 29 extending through the annular member 26. A seal carried by the member 26 forms a seal around the piston rod.

As here shown, the piston rod 29 is made up of concentric tubular members 31 and 32 providing fluid passages 33 and 34, leading into the cylinder above and below the piston 28 respectively. The upper end of the piston rod 29 is supported by a partition 35 which is xed in the upper part of the body 4portion 23. Passages 33 and 34 in the partition 35 are arranged to register with the passages 33 and 34 in the piston rod. Hydraulic uid under pressure when directed through the passages 33 and 33 will enter the cylinder 23 above the piston 28 to cause the cylinder 25 to be retracted into the body portion 23, while uid below the piston is exhausted through passages 34 and 34 back to the source of hydraulic uid under pressure. When hydraulic duid under pressure is directed through the passages 4' and 34 into the cylinder 25 below the piston 28 the cylinder will be extended while uid above the piston will return to the source through passages 33 and 33.

Each of the jacks 15 and 16 is controlled by a manually operable valve 36 mounted thereon and connected by means of la conduit 41 with the passages 33 and 33 in the jack. A similar conduit 42 connects the valve 36 with the passages 34 and 34 in the jack. An intake manifold 39 and a return manifold 44 are mounted on each side wall of the shield and through exible hose lines and 43 respectively are connected to the valves 36 for the adjacent pair of jacks as indicated by the schematic showing in FIG. 5. As shown in FIGS. 1 and 2, the manifolds 39 and 44 are connected to intake and `return conduits 45 and 46 which may be connected to any suitable source of hydraulic fluid under pressure, not shown.

This arrangement of manifolds, conduits and control valves is merely illustrative and it is to be understood that any suitable hydraulic circuitry may be employed for the jacks provided each jack is equipped with valve means operable at will to extend or retract each jack independently ofthe other jacks.

Each of the jacks 15 and 16 is constructed so that piston unit 24 and the cylinder 25 may be removed and 6 replaced relative to the tubular body portion 23 of the jack, also so that an air blast may be applied to the interior of the body to clean out any foreign matter that may collect between the opposed walls of the body portion 23 and the cylinder 25. Accordingly, as best shown in FIG. 6, the piston rod 29 is held in an opening 47 in the partition 35 by means of a set screw 48, the removal of which makes it possible to remove the piston unit and the cylinder. With reference to use of an air blast for removing foreign matter, a normally plugged passage 49 leading through the partition 35 into the portion of the tubular body 23 below the partition provides for this operation. When the plug in the outer end of the passage 49 is removed an air blast may be directed into the body 23 through passage 49 for the purpose above stated.

A modilied form of jack M embodying this invention which may be used in groups of two or more on each side of the shield is shown in FIGS. 8 and 9, if desired, in place of the jacks 15 and 16. This jack is similar to the jacks 15 4and 16 shown in FIG. 5, except for the use of the upper part thereof as a reservoir R for hydraulic fluid and the use of two manually operable pumps R1 and R2 mounted on the jack and operable for effecting extension and retraction of the jack. The pumps R1 and R2 are provided with valves V1 and V2, respectively, for controlling flow through the pumps. As the jack M is other- Wise of the same construction as the jacks 15 and 16 and mounted on the shield 5 in the same manner as the jacks 15 and 15, the same reference characters that are applied to the jacks 15 and 16 and to the mounting means therefor are applied to the jack M.

The hydraulic circuit shown in FIG. 9 includes a supply line 59 leading from the reservoir R on the top of the jack M to the hand pump R1, which latter, when the valve V1 is in the position shown, may be operated to force uid under pressure through a line 51 to passages 34' and 34 and below the piston 29, thereby extending the cylinder 25. The return uid from the above piston 29 passes through passages 33 and 33', and line 53 leading to the pump R2, which latter, in view of the position of valve V2, will route the return uid through return line 54 leading to the reservoir R. When the pump R2 is operated with the valve V2 turned to occupy the position of the valve V1 shown in FIG. 9, fluid from supply line 59a leading from line 50 is pumped through line 53, passage 33' and 33 into the cylinder 25 above the piston 29, thereby retracting the cylinder 35 and causing return ow from below the piston through passages 34 and 34', line 51, valve V1. At this time the valve V1 is turned to occupy the same position as the valve V2 in FIG. 9 so the return flow will pass through lines 55 and 54 leading to reservoir R,

The apparatus of this invention includes a plurality of air operated rams 60 securely anchored to the shield S and provided with brackets 61 for supporting breast boards 62. These rams in being air operated rams will yield as the shield is advanced as the breast boards 62 are firmly held by the rams against the tunnel face F and thereby prevent cave-in of this face.

With reference to the foregoing description and accompanying drawings, it will be apparent that this invention provides a novel method of driving a tunnel into the earth with an elongate arched shield and a plurality of supports disposed on each side of the longitudinal center of the shield in such a manner that the shield is longitudinally movable relative to the supports and the supports may be longitudinally moved relative to the shield. In supporting each side of the shield with a group of shiftable supports or jacks in accordance with this invention, the jacks may be shifted one or more at a time into positions best to support the shield but in all instances so that other of the jacks on each side of the shield afford adequate support for opposite sides of the shield at all times. With this arrangement and method of disposing and shifting the jacks, a better positioning thereof for support of the shield in soft, wet or what is known as had ground may be effected. Moreover, the length of each leg may be varied while it is in ground engaging and shield supporting position by extending certain jacks and retracting others. This will make it possible to tilt or cant the shield with a nicety so as to facilitate making accurate turns of the tunnel bore while remaining on grade. lf it is desired to provide a greater number of jacks at a speciiic location on one side of the shield that is longitudinally spaced from a lesser number of jacks on the opposite side of the shield to compensate for bad ground or for any other purpose, this arrangement readily may be brought about. Not only will the foregoing advantages he afforded by utilizing a plurality of jacks on each side of the shield in the manner herein described, without use of a center jack, but greater Working space is provided at the face of the tunnel to facilitate the operation of forming the tunnel.

While specific structural details have been shown and described, it should be understood that changes and alterations may be resorted to without departing from the spirit oi the invention as defined in the appended claims.

I claim:

1. A method of driving an elongate, arched shield into the ground in the formation of a tunnel comprising: positioning the shield so that one end thereof may be progressively driven into the ground; providing on each side of the longitudinal center line orF the shield and adjacent said end and each side of the shield a plurality of supports in Contact with the ground and with the upper portion of the interior of the shield at longitudinally spaced locations on the shield; applying a force for moving said shield longitudinally relative to said supports to advance the shield into the ground; removing the supports one at a time from contact with the ground: moving each support longitudinally of the shield to a new position when free of the ground while other of said supports on opposite sides of said center line remain in contact with the ground; and reengaging each support with the groundl following repositioning thereof.

2. A method of driving an elongate, arched shield into the ground in the formation of a tunnel comprising: positioning the shield so that one end thereof may be progressively driven into the ground; providing on each side of the longitudinal center line of the shield and adjacent said end and each side of the shield a plurality of supports in contact with the ground and with the upper portion of the interior of the shield at longitudinally spaced locations on the shield; applying a force for moving said shield longitudinally relative to said supports to advance the shield into the ground; removing the supports one at a time from Contact with the ground alternately from opposite sides of said center line; moving each support longitudinally of the shield to a new position when free of the ground While other of said supports on opposite sides of said center line remain in contact with the ground; and reengaging each support with the ground following repositioning thereof.

3. A method of driving an elongate, arched shield into the ground in the formation of a tunnel which includes the steps of: positioning the shield so that one end may be driven progressively into the ground; providing beneath the shield along each side of the longitudinal center line thereof and adjacent said end and opposite sides of the shield a plurality of supports in engagement with' the interior or the -upper part of the shield as well as in supporting engagement with the ground beneath the shield; applying a force for moving said shield longitudinally relative to said supports to cause said shield to advance into the ground; and intermittently moving said supports one at a time forwardly toward said end of the shield while the other supports remain fixed for supporting the shield on opposite sides of said center line.

4. The method of driving an elongated tunnel shield including: supporting said shield on a pair of transversely spaced rows of vertical supports adjacent the sides of said- 2? shield; moving said shield longitudinally relative to said supports; and then moving said supports one at a time to a new position in its row while the shield is supported adjacent said sides thereof by the other of said supports and maintained in its proper position transverscly of the tunnel.

5. A method of forming a tunnel comprising the steps of: positioning an elongate, arched shield so that it may be progressively driven into the ground; provi-ding on each side of the longitudinal center line of the shield a plurality of extensible and relractible supports for engaging the ground and the shield to support the shield; erecting a tunnel wall structure within one end of the shield rearwardly of said supports; applying a force to said shield to move it longitudinally relative to said supports and said wall structure so as to advance the shield into the ground; retracting said supports one at a time from engagement with the ground following said advance of said shield and while other of said supports on opposite sides of said center line support opposite sides of the shield; moving each retracted support longitudinally to a new position while other or' the supports on opposite sides of said center line support the shield; extending each support when repositioned into engagement with the ground; erecting an addition to said wall structure in said shield rearwardly of said repositioned plurality of supports on opposite sides of said center line; and again applying a force for further advancing said shield into the ground relative to said repositioned supports and said wall structure.

6. A method of forming a tunnel comprising: positioning an elongate, arched shield so as to be progressively driven into the ground; providing within the shield in laterally spaced relation to the longitudinal center line of the shield and adjacent each side wall of the shield a plurality of supports extending longitudinally in a row with the supports in each row engaged with the shield and the ground therebeneath on opposite sides of said center line in the forward portion only of said shield; applying to the shield a force for moving it longitudinally relative to said supports to advance the shield into the ground; moving said supports one at a time after said advance of said shield to a new shield supporting position while other of said supports in each row remain in position to support opposite sides of the shield; erecting a tunnel wall structure within the rearward portion of said shield; and applying a force to again advance said shield into the ground.

7. A method of driving a shield into the earth in the formation of a tunnel including the steps of: positioning an elongate, arched shield so that it may be driven into the earth; providing within the shield in laterally spaced relation to the longitudinal center line of the shield along each side wall of the shield a plurality of supports extending in a row with the supports of each row engaged with the shield and the ground therebeneath on opposite sides of said center line; applying to the shield a force for moving it relative to said supports to advance the shield into the earth; moving said supports to reposition them relative to said shield one at a time after said advance of the shield, alternately from the rows on opposite sides of said center line while at least one of said supports in each row remains in position to support opposite sides of said shield; and thereafter applying a force to further advance the shield into the earth.

8. The method of driving a shield into the earth in the formation of a tunnel including the steps of: positioning an arched shield so that it may be driven into the earth; providing within the shield in laterally spaced relation to the longitudinal center line of the shield adjacent each side Wall of the shield a plurality of supports extending in a row axially of the shield with each support engaged with the shield and the ground therebeneath; applying to the foremost of said supports in each of said rows a force for restraining said support and the supports rearwardly thereof in each row against forward movement during advance of the shield into the earth; applying to the shield a force for advancing it into the earth relative to said supports and independently and selectively applying to the supports rearwardly of the foremost supports of each row a force for restraining the rearward supports against movement while repositioning the forward supports.

9. The method of driving a shield into the earth in the formation of a tunnel including the steps of: positioning an arched shield so that it may be driven into the earth; providing within the shield in laterally spaced relation to the longitudinal center line of the shield adjacent each side wall of the shield a plurality of supports extending in a row axially of the shield with each support engaged with the shield and the ground there-beneath; applying to the foremost of said supports in each of said rows a force for restraining said support and the supports rearwardly thereof in each row against forward movement upon advance of the shield into the earth; applying to the shield References Cited UNITED STATES PATENTS 2,997,853 7/1961 Kemper 61-85 FOREIGN PATENTS 910,770 1954 Germany. 1,089,710 1960 Germany.

JACOB SHAPIRO, Prz'mmy Examiner..

UNITED STATES PATENT oFEICE CERTIFICATE OF CORRECTION Patent No. 3,373,572 March l9, 1968 Maxwell F. Kemper It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 26, "position" should read portion H' line 5l, "4l" should read 34'".

Signed and sealed this 19th day of August 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR. 

1. A METHOD OF DRIVING AN ELONGATE, ARCHED SHIELD INTO THE GROUND IN THE FORMATION OF A TUNNEL COMPRISING: POSITIONING THE SHIELD SO THAT ONE END THEREOF MAY BE PROGRESSIVELY DRIVEN INTO THE GROUND; PROVIDING ON EACH SIDE OF THE LONGITUDINAL CENTER LINE OF THE SHIELD AND ADJACENT SAID END AND EACH SIDE OF THE SHIELD A PLURALITY OF SUPPORTS IN CONTACT WITH THE GROUND AND WITH THE UPPER PORTION OF THE INTERIOR OF THE SHIELD AT LONGITUDINALLY SPACED LOCATIONS ON THE SHIELD; APPLYING A FORCE FOR MOVING SAID SHIELD LONGITUDINALLY RELATIVE TO SAID SUPPORTS TO ADVANCE THE SHIELD INTO THE GROUND; REMOVING THE SUPPORTS ONE AT A TIME FROM CONTACT WITH THE GROUND: MOVING EACH SUPPORT LONGITUDINALLY OF THE SHIELD TO A NEW POSITION WHEN FREE OF THE GROUND WHILE OTHER OF SAID SUPPORTS ON OPPOSITE SIDES OF SAID CENTER LINE REMAIN IN CONTACT WITH THE GROUND; AND 